A mobile communication device may be capable of making and receiving voice and/or video calls and/or sending and receiving data over a wireless communication network. Before it is able to do this, the mobile station has to select a communication network and register on it. The procedures of Network Selection and Location Registration are included among the Idle Mode procedures and are performed on signaling channels.
In a given geographical location (such as a country or a town), typically there are simultaneously many mobile network operators. These network operators include, but are not limited to, operators who provide mobile services using GSM, GPRS, EDGE, CDMA and UMTS technologies or their variants. These network operators provide services, such as voice and data services, to their own subscribers and to subscribers from other networks, said latter subscribers being referred to as “roamers”. When the network operator provides services to a roamer from a foreign country, it is referred to as “international roaming”. When the network operator provides services to a subscriber from another network in the same country, it is referred to as “national roaming”.
The network with which a subscriber has a subscription and, as a consequence, a direct billing relationship is referred to as the Home Public Land Mobile Network (HPLMN or Home Network) and it is operated by the Home Operator. To the purpose of the present description, the terms Operator and Network are in general interchangeable. If the subscriber is in a network with which it does not have a subscription and a direct billing relationship, the serving network is referred to as the Visited Public Land Mobile Network (VPLMN), and the subscriber is referred to as an in-roamer by the VPLMN. The same subscriber is referred to as an out-roamer by the HPLMN. A roaming agreement is required between the two PLMNs, including both technical topics (signaling and traffic connections establishment, etc.) and commercial topics (Inter Operator Tariffs, billing arrangements, SLAs and so on). The in-roamers are treated as temporary subscribers from a service availability perspective, while the billing for usage incurred by them is through inter-carrier settlements via the home network of the subscriber. In the following, the term “roam” will be used also for mobile terminals or users, that are attempting to register on a network other than the Home Network.
When “home” subscribers roam into visited networks, they may roam onto one of the plurality of communication networks which are available within the relevant geographic coverage area and have a roaming agreement with the home network. “Network Selection” or “PLMN Selection” is the particular process performed by the mobile station for selecting the one communication network over which to register and operate.
The standard specification TS 23.122 V6.4.0 (2005-03) “Technical Specification Group Core Network; NAS Functions related to Mobile Station in idle mode” from the 3GPP describes the PLMN Selection procedure for the mobile standard Global System for Mobile Communication (GSM).
In automatic network selection mode the mobile terminal automatically uses a set of rules to find the network to register with. Industry specifications state a possible order of these rules as:
1. The last selected network (from Elementary File “EF-LOCI” on the SIM card);
2. The Home Network if it's available (based on MCC and MNC from IMSI);
3. If the last registered network is not found, the mobile terminal tries to register on the list of networks from the Preferred PLMN Lists that is stored in memory (e.g. “EF-PLMNSEL” on SIM card) in priority order excluding the previously selected PLMN;
4. Other PLMN with a received signal level above a given threshold in random order excluding the previously selected PLMN; and
5. Any other PLMN excluding the previously selected PLMN in order of decreasing signal strength.
In manual network selection mode, the mobile terminal displays a list of available networks to the user. The user selects one of them and the mobile terminal attempts registration onto that network. If the registration is not successful, the mobile terminal shows the list of networks to the user once again. In manual mode, the user performs the selection of a particular network with no or few information about the available networks.
Over the last few years, traffic (and high-margin revenues from roamers) related to wireless services in roaming scenarios is matching a continuous growth as mobile penetration in local markets increases and people more often travel for business and vacation. Various network operators have partnership agreements with each other (alliances) that include more favorable roaming charges than non-partners receive. As a consequence, there is a tendency for network operators being interested in controlling the process of PLMN selection to protect the existing roaming revenues and grow them further and to give the best service experience to the subscribers even when roaming.
A commonly-used method of attempting to prevent roaming subscribers from registering with non-preferred networks includes storing lists of preferred networks on a SIM in the subscriber's mobile terminal (such as the Preferred PLMN lists). The list can be burned on the SIM or updated using Over-The-Air (OTA) messages. This list influences the initial selection of the preferred network. Disadvantages coming from the above Preferred PLMN lists are the consumption of memory SIM resources (which may in turn prohibit the storing of the list in legacy SIM having low memory), the consume of network resources for their upgrading, the fact of being equal for all the users.
To counteract the fact that, due to various reasons (for example, the preferred network is not currently available or loses coverage), the mobile terminal may also select a non-preferred network (e.g. steps 4 or 5 above) and remain there unless the non-preferred network loses the radio coverage (even when the handset is powered off, the non-preferred network stays on the SIM card and oh next power on it will be selected according to step 1 above), PLMN selection techniques are known which allow the Home Operator to control the Visited PLMN choice on which the roaming user registers, by way of prohibiting the registration to the attempted network in case the request originates from a network not preferred by the Home Operator or forcing a new registration if the mobile terminal is already registered on a network not preferred by the Home Operator. Using an apparatus in the Home network, the signaling originating from an out-roamer is intercepted and a Home-preferred Operator selection is forced. It is also contemplated the possibility to update suitable files present on the SIM (e.g. PLMNSEL, LOCI e FPLMN), via OTA, typically using a SIM Application Toolkit. See for example WO2004/014101 “Method and System for Cellular Network Traffic Redirection”, WO2004/066663 “Roaming Method” and U.S. 2004/0192306 “Preferred Network Selection”.
In WO 02/32181 “Method and system for selecting service provider based on roaming charges”, a user, through using a program application for roaming existing in a mobile telephone, specifies which operator is most cost-effective for voice call at a given point in time.
U.S. 2005/0037755 describes a network selection technique for a mobile communication device which provides several different features and functions which require associated network services, such technique taking into account the availability of all of these services. The mobile device identifies one or more communication networks available for communication within a geographic coverage area, using a conventional scanning operation. Next, the mobile device identifies one or more communication services made available by each one of these communication networks, for example at least in part by actually attempting to access the service in the network. Next, the mobile device selects communication networks in a prioritized fashion based on the communication services that are made available by it. If assigning priorities, the mobile device preferably keeps a prioritized network list of networks from the “best” to “worst”. The “best” network may be the one that provides the greatest number of communication services for the mobile device or the one that provides the greatest number of preferred communication services for the mobile device. Here, the one or more preferred communication services may be predefined by the network, predefined by the mobile device manufacture (stored in the device's memory), or predefined by the end-user who programs such service priorities via the user interface. In another variation, each communication service is preassigned a relative weight value and a sum of relative weight values for available communication services in each network is calculated. Here, the “best” network having the largest sum of weight values is kept at the top of a prioritized network list. Additional weightings may be used as well for these decision-making process, including success rate, data throughput rate (specified or actual), and cost.